PATHWAYS: MOVEMENT AND PATHWAYS: MOVEMENT AND SENSATIONSENSATION

Emily BurtenshawEmily BurtenshawDr Pedro Amarante AndradeDr Pedro Amarante Andrade

THE PATHWAYSTHE PATHWAYS

A neural pathway connects one part of the nervous system with another

via a bundle of axons.

MotorEfferent

SensoryAfferent

THE PATHWAYSTHE PATHWAYS

MOTOR SYSTEM MOTOR SYSTEM

MOVEMENT OVERVIEWMOVEMENT OVERVIEW

• Complex and incompletely understood• Planned in sensorimotor areas of the cortex• Is effected by pathways of descending neurons,

under the control of the cerebellum and the basal ganglia

• Control is achieved through sensory feedback from muscles/joints

• And information from the eyes and ears (vision and balance) also influences the motor pathways

MOVEMENT OVERVIEWMOVEMENT OVERVIEW

• Complex and incompletely understood• Planned in sensorimotor areas of the cortex• Is effected by pathways of descending neurons,

under the control of the cerebellum and the basal ganglia

• Control is achieved through sensory feedback from muscles/joints

• And information from the eyes and ears (vision and balance) also influences the motor pathways

http://7e.biopsychology.com/vs11.html

MOVEMENT OVERVIEWMOVEMENT OVERVIEW

Biological Psychology: An introduction to Behavioural, Cognitive, and Clinical Neuroscience.

S. Marc Breedlove, Simon Watson

MOVEMENT OVERVIEWMOVEMENT OVERVIEW

• Complex and incompletely understood• Planned in sensorimotor areas of the cortex• Is effected by pathways of descending neurons,

under the control of the cerebellum and the basal ganglia

• Control is achieved through sensory feedback from muscles/joints

• And information from the eyes and ears (vision and balance) also influences the motor pathways

LOCATION OF THE BASAL GANGLIALOCATION OF THE BASAL GANGLIA

https://kin450-neurophysiology.wikispaces.com/

Basal+Ganglia+II

http://antranik.org/cerebral-white-matter-and-gray-matter-and-basal-ganglia/

CONTROL CIRCUITSCONTROL CIRCUITS• The CEREBELLUM: coordinates

motor and sensory information• Gets info from the cortex about

what muscles SHOULD be doing, and compares this with what is ACTUALLY happening

• The basal ganglia: involved in control of background movement, and initiation of movement patterns

Biological Psychology: An introduction to Behavioural, Cognitive, and Clinical Neuroscience.S. Marc Breedlove, Simon Watson

VOLUNTARY MOVEMENTVOLUNTARY MOVEMENT

• Although skeletal movement is under our voluntary control, much of it is automatic

• Speech, chewing, swallowing comes under the heading of automatic movements that can be altered voluntarily

• Can be affected by developmental abnormalities or acquired brain injury

CORTICAL ANATOMY OF THE MOTOR CORTICAL ANATOMY OF THE MOTOR SYSTEMSYSTEM

http://www.sofiatopia.org/equiaeon/ibrain12.jpg

Blood flow to this region

increases prior to

movement actually

occurring suggesting a

role in planning the movement

flow

FUNCTIONAL DIVISIONS OF THE MOTOR FUNCTIONAL DIVISIONS OF THE MOTOR SYSTEMSYSTEM

• Final common pathway (FCP): • LMNs: generates activity in skeletal (voluntary) muscles

VOLUNTARY

INVOLUNTARY

FUNCTIONAL DIVISIONS - MOTOR SYS.FUNCTIONAL DIVISIONS - MOTOR SYS.SYSTEMS TRACTS ORIGIN TO

PYRAMIDALCorticobulbar

CortexCranial nerves

(Brainstem)

Corticospinal

Spinal cordEXTRAPYRAMIDAL

Rubrospinal Red nucleus

Pontine reticulospinal Reticular

formationMedullary reticulospinal

Lateral vestibulospinal Vestibular nuclei

Tectospinal Midbrain tectum

http://humanphysiology.academy/Neurosciences%202015/Chapter%205/A.5p%20Cerebellar

%20Pathways.html

FUNCTIONAL DIVISIONS - MOTOR SYS.FUNCTIONAL DIVISIONS - MOTOR SYS.

FUNCTIONAL DIVISIONS - MOTOR SYS.FUNCTIONAL DIVISIONS - MOTOR SYS.

Wikicommons. Polarlys and Mikael Häggström.

THE CORTICAL AREAS RESPONSIBLE FOR THE CORTICAL AREAS RESPONSIBLE FOR MOVEMENT AND SENSATIONMOVEMENT AND SENSATION

• What is meant by a motor/sensory homunculus?– What areas have the most representation?– What are the main differences you notice between

the two homunculi?

THE MOTOR CORTEX INVOLVEMENT IN THE MOTOR CORTEX INVOLVEMENT IN SPEECHSPEECH

The primary motor cortex is somatotopically arranged in the precentral gyrus with the

body represented upside down and individual areas

represented out of proportion to their actual size

Note that disproportionately more cortex devoted to the movements of the muscles involved in speech

THE DIRECT PATHWAYSTHE DIRECT PATHWAYS

DIRECT DIRECT PATHWAYSPATHWAYS

PYRAMIDAL CELLSPYRAMIDAL CELLS

SO..THE DIRECT ACTIVATION PATHWAY…SO..THE DIRECT ACTIVATION PATHWAY…

• Originates in the (predominantly) frontal cortex of each hemisphere

• Directly connects this cortex to the lower motor neurons• The upper motor neurons synapse on:

– anterior horn cells (corticospinal tract)– cranial nerve nuclei (corticobulbar tract)

• The lower motor neurons emerge at the spinal and bulbar levels, and activate skeletal muscle

• The direct activation pathway is primarily facilitative• Activity leads to finely controlled, skilled and discrete

movements• The ‘express’ route

THE CORTICOSPINAL TRACTTHE CORTICOSPINAL TRACT

www.studyblue.com

THE THE CORTICOBULBAR CORTICOBULBAR TRACTTRACT

www.eyesthetica.com

THE CORTICOBULBAR TRACTTHE CORTICOBULBAR TRACTThe axons of the UMNs follow the same path as those of the corticospinal tract until they reach the brainstem, there

some cross over, others remain uncrossed

The UMNs terminate in the nuclei of

CN III IV V VI VII IX X XI and XII

HIND BRAIN + HIND BRAIN + BRAINSTEMBRAINSTEM

NUCLEINUCLEI

http://www.nature.com/gimo/contents/pt1/fig_tab/gimo2_F2.html

CN nuclei lie at the same

level that the nerve enters or leaves the brainstem

NUCLEINUCLEI

http://what-when-how.com/neuroscience/the-cranial-nerves-organization-of-the-central-nervous-system-part-1/

INDIRECT ACTIVATION PATHWAYSINDIRECT ACTIVATION PATHWAYSSometimes called extrapyramidal pathway•Complex and incompletely understood (esp with regard to speech pathways)•Originates in motor, premotor and sensory cortex, and brainstem•Composed of numerous short pathways and interconnected structures (so are polysynaptic) involving the motor cortex, the basal ganglia, the limbic system, the thalamus, the cerebellum, the reticular formation AND nuclei in the brainstem

• UMNs synapse • Helps regulate reflexes & mediates

subconscious automatic muscle activities e.g. posture and tone

• Many of its activities are inhibitory (i.e. prevent too much tone/movement)

• The ‘local’ route

INDIRECT ACTIVATION PATHWAYSINDIRECT ACTIVATION PATHWAYS

EXAMPLES OF INDIRECT PATHWAYSEXAMPLES OF INDIRECT PATHWAYS• Rubrospinal - large muscle movement as well as fine motor

control. Terminates cervical spinal cord. Facilitates flexion in the upper extremities

• Reticulospinal - descends from reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb muscles. Involved mainly in locomotion and postural control

• Tectospinal - coordinates head and eye movements. Connects midbrain tectum and spinal cord. Mediates reflex postural movements of head in response to visual and auditory stimuli

EXAMPLES OF INDIRECT PATHWAYSEXAMPLES OF INDIRECT PATHWAYS• Vestibulospinal – Vestibular nuclei receive information

through vestibulocochlear nerve about changes in orientation of head. The nuclei relay motor commands through the vestibulospinal tract. Function of these motors commands = to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head.

EXPIRAMIDAL PATHWAYSEXPIRAMIDAL PATHWAYS

SENSORY SYSTEM SENSORY SYSTEM

SENSORY SYSTEMSENSORY SYSTEM

Organ

Ganglion CNS –Cortex

CNS – Thalamus

CNS – Spinal cord

3 or more neurons

SUMMARY OF DIRECT AND INDIRECT SUMMARY OF DIRECT AND INDIRECT ACTIVATION PATHWAYSACTIVATION PATHWAYS

• Both pathways end on LMNs• These LMNs receive both excitatory and inhibitory

stimulation from both pathways• The sum of this input determines the final response of

an individual neuron in the pathway• The indirect pathway provides the framework (muscle

tone, posture, regulation of reflex activity)• The direct pathway accomplishes the skilled, discrete

muscle actions • The LMNs are referred to as the final common

pathways or FCP

WHITE MATTER PATHWAYSWHITE MATTER PATHWAYS

There are three types of white matter pathway:• Commissural• Association• Projection

WHITE MATTER WHITE MATTER PATHWAYSPATHWAYS

WHITE AND GREY MATTERWHITE AND GREY MATTER• White matter = highways for information flow

in the NS• Grey matter = receives and integrates

incoming and outgoing information

Greymatter

White matter

COMMISSURALCOMMISSURAL WHITE MATTER WHITE MATTER PATHWAYSPATHWAYS

• Commissural white matter pathways connect the 2 hemispheres. The largest is the corpus callosum, with its posterior splenium, central body or trunk, anterior genu, and ventrally directed rostrum.

• Besides the corpus callosum, commisural white matter pathways include the anterior commisure which connects the olfactory &

temporal regions, and the posterior commisure

ASSOCIATIONASSOCIATION WHITE MATTER PATHWAYS WHITE MATTER PATHWAYS• Connect cerebral areas within each hemisphere

(generally bidirectional)• Contain short association fibres known as "U"

or arcuate fibres that link adjacent cortical gyri • Long association fibres, all of which terminate in

the frontal lobe are: the cingulate, the arcuate fasciculus, the superior occipitofrontal fasciculus, the inferior occipitofrontal fasciculus, and the uncinate fasciculus

PROJECTIONPROJECTION WHITE MATTER PATHWAYS WHITE MATTER PATHWAYS

• White matter projections consist of long tracts which connect the cortex with the brainstem and spinal cord

• These long tracts both ascend and descend. • The corona radiata consists of projection tracts

running to and from the cortex• The projections converge at the internal capsule

www.leonidzhukov.ru

STUDY THE STRETCH REFLEXSTUDY THE STRETCH REFLEX

• Revise the structure and function of the muscle spindle (see lecture 3, Nerves, Muscles and How They Work)

• Watch the video or review the pathways involved in the stretch reflex:

• http://www.youtube.com/watch?v=HfuhVWK8C0U

NOTE THE TERMS:NOTE THE TERMS:

• Agonist/antagonist• Interneuron• Reciprocal innervation

• If you are unfamiliar with these terms through your reading, then look them up and write some definitions now

PARTICULAR RELEVANCE TO SLTPARTICULAR RELEVANCE TO SLT• To perform accurate movements, information re

the range, rate and force of contraction, and position of the muscles, is essential.

• Muscle spindle actions are involved in controlling the rapid and fine muscle movements required for speech.

• Sensory nerves from muscle spindles send out a continuous stream of impulses to the CNS

• Muscle tone is maintained via these feedback mechanisms

www.bio.davidson.edu

Why does this reflex involve contralateral pathways?

CASE 1:CASE 1:JANE, 17, SUFFERED A C7 SPINAL CORD JANE, 17, SUFFERED A C7 SPINAL CORD

INJURY AFTER FALLING FROM HER HORSEINJURY AFTER FALLING FROM HER HORSE

• Will she exhibit a knee jerk reflex when the patellar tendon is stretched?

• What will she feel?

SOME CLUESSOME CLUES

• You will need to refer to the pathway in this particular stretch reflex, and consider the spinal level involved

• You will need to research the main sensory pathways which run from the periphery

to the cortex• Then consider how spinal injury might affect these pathways

The diagram illustrates the position of the major ascending (sensory) and descending (motor) tracts in the

upper spinal cord

Case 2: Joyce, 74, has had a stroke. Case 2: Joyce, 74, has had a stroke. The CT scan shows an infarct in the posterior The CT scan shows an infarct in the posterior

limb of the left internal capsule limb of the left internal capsule • What will be the likely effects of this stroke?• Will her signs and symptoms be of upper

motor neuron or lower motor neuron damage?

• Will they be contralateral or ipsilateral to the lesion side?

• List the common signs of both upper and lower motor neuron damage

THE CLUETHE CLUE

• Lies in the direct pathway… study this closely and identify the internal capsule….you may need to magnify (hint!)

“Elementary, my dear Watson!”

www.stanfordmedicine25.stanford.edu

AN EXAMPLE OF SOMATOTOPIC AN EXAMPLE OF SOMATOTOPIC ORGANISATIONORGANISATION

BELL’S PALSYBELL’S PALSY

• Why is it called Bell’s palsy?• What causes it?• Where is the lesion? • Use the ppt slides supplied, your texts and

watch the You Tube materials on the following slides to help you

• Can it be treated?

HERE IS YOU CLUEHERE IS YOU CLUE

www.nature.com

AND MORE CLUES…..AND MORE CLUES…..

Unilateral UMN v Bells’ palsyhttp://www.youtube.com/watch?v=L8hIWPYm6VE•http://www.youtube.com/watch?v=Up-oOhRO1N0An explanation of the origin of bulbar v pseudobulbar palsy

LATERAL MEDULLARY SYNDROMELATERAL MEDULLARY SYNDROME

• What part of the medulla is affected?• Why does the patient lose pain and temperature

sensation on the opposite side of the body to the lesion, but on the same side of the face as the lesion?

• What are some possible causes?• What are the other symptoms?

SLTs can be involved in the care ofpeople with lateral medullary syndrome